准噶尔盆地西北缘稠油分布的地质规律及成因探讨

An approach to the distribution and origin of heavy oil in the northwest margin of Junggar basin.

准噶尔盆地西北缘稠油分布范围广，埋藏浅，含油层位多，沿地层超覆不整合面叠瓦状分布。构造、盖层、地层水等地质因素制约了稠油的平面分布，并影响了原油的稠变历程。该区稠油经历了运移阶段和成藏后阶段两次稠变过程，尤其是成藏后阶段的水洗、氧化、生物降解等对原油的稠变作用很显著。结合该区构造发展史，认为印支运动和燕山运动分别导致了三叠系稠油油藏和侏罗系稠油油藏的形成。三叠系稠油是三叠系稀油油藏成藏后，在侏罗系沉积前遭破坏而形成的；侏罗系稠油则是三叠系油藏的原油在再次运移过程中稠变的结果，一些地区齐古组隔层被剥蚀，使稠油成藏后进一步稠化。图４参４（梁大新摘）

The northwest margin of Junggar basin contains rich heavy oil resources. It is the most important thermal recovering heavy oil area in Junggar basin. By analysis and study of heavy oil distribution and geologic conditions of each heavy oil area, this paper considers that geologic factors, such as structure, caprock and formation water, clearly related to areal distribution of heavy oil, affected different thichened courses of crude oil. Origin study shows that heavy oil in northwest margin underwent 2 thichened courses, that are, migration phase and reservoir forming phase. Especially, water washing, oxidation and biodegradation in the reservoir forming phase strikingly reworked heavy oil. On the basis of above study, combined with tectonic history of the northwest margin, the paper considers that Indosinian movement resulted in Triassic heavy oil reservoirs, and Yanshan movement formed Jurassic heavy oil reservoirs. Triassic heavy oil reservoirs were formed from the destruchtion of Triassic paleo normal oil pool , before the Jurassic formation depossited . Jurassic heavy oil is the result of viscosifying of oil from Triassic paleo pools during its re migration . Because of the erosion to Qigu Formation barrier , some heavy oils were viscosified after their pool forming .